title: In-syringe magnetic-stirring-assisted liquid-liquid microextraction for the spectrophotometric determination of Cr(VI) in waters.
abstract: A fully automated method for the determination of chromate is described. It is based on the selective reaction of Cr(VI) with diphenylcarbazide in acidic media to form a colored complex of Cr(III) with the oxidation product diphenylcarbazone. The reaction was performed within the syringe of an automatic burette containing a magnetic stirrer for homogenization of the sample and the required reagents. In-syringe stirring was made possible using a specially designed driving device placed around the syringe barrel to achieve a rotating magnetic field in the syringe, forcing the stirrer to spin. In a second step, the reaction mixture in the syringe was neutralized to allow in-syringe magnetic-stirring-assisted dispersive liquid-liquid microextraction of the complex into 125 μL of n-hexanol. After phase separation by droplet flotation over 30 s, the organic phase was propelled into a coupled spectrophotometric detection cell. The entire multistep procedure including in-system standard preparation was done within 270 s. The method was used for the analysis of natural waters, achieving average analyte recovery of 103%, a limit of detection of 0.26 μg L(-1), and a repeatability of less than 4% relative standard deviation.
authors.affiliation: Laboratory of environmental Analytical Chemistry, University of the Balearic Islands, Carreterra de Valldemossa km 7.5, 07122, Palma de Mallorca, Spain.
authors.forename: Camelia
authors.initials: C
authors.lastname: Henríquez
authors.forename: Burkhard
authors.initials: B
authors.lastname: Horstkotte
authors.forename: Petr
authors.initials: P
authors.lastname: Solich
authors.forename: Víctor
authors.initials: V
authors.lastname: Cerdà
mesh_terms: D002857:Chromium / Q000032:analysis* / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D059627:Liquid Phase Microextraction / Q000295:instrumentation*; D008280:Magnetics / Q000295:instrumentation*; D008904:Miniaturization; D015203:Reproducibility of Results; D012212:Rheology / Q000295:instrumentation*; D012680:Sensitivity and Specificity; D013053:Spectrophotometry / Q000295:instrumentation*; D013594:Syringes; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D002857:Chromium